Here are some gut shots...apologies for the photo quality. Pots are PEC, signal caps are 225P ODs, blue pF caps are Murata ceramic, black 20uF filters are Sprague Atom 350v (I realize that when totally unloaded the amp will be at ~360vdc...sue me ), 200uF cathode cap/25uF cathode cap are Sprague Atom 50v, and the black dual cap is an F&T 33uFx2/450v. My treble cap is a parallel combo of a 47pF Murata ceramic and a CD 10pF silver mica (I guess I figured that being a little high was better than being a little low ). I used the Heyboer PT and Dagnall choke that RJ bought for the group but used a Mercury Magnetics Woden clone OT (it only has 8 and 16 ohm taps). I used a fused IEC connector for the mains and then used the fuse holder for the HT fuse. I paralleled the triodes in the first tube for the input stage (and adjusted the values...this is all a test to see which way I like best...values/paralleling may change ) and then used Marshall-style wiring on V2 (except reversed the triodes). And of course the layout is different. Other than that it's exactly like a Rocket.
EDIT: I also added two .1uF ODs to the power board (one in parallel with the F&T caps and the other in parallel with the PI filter)...and there is also an extra 330K/3W resistor to ground (bleeder resistor) from the screen node. These are just my own additions.
just wondering if there is a consensus yet on a layout for the group build. What is the skinny on the John Speck/Paul Ruby " Rocket ". How different is that to KF.
Awesome work... I actually looked at those OT's and talked with Patrick at Mercury about them. He declared they are awesome!
That is really a sweet build...
Ange,
I'm up late and after I finish gawking at the Matt build, I'll be working on a layout. I have to say I'll be watching Matt's lead as I work on that layout... hope to have something up for review soon.
the old russian military is very difficult to beat due
to its robust nature and sonic value ..i have quads
matched for 42 dollars or pairs for 25 shipping is
about 2 bucks paypal is tkilgore@tubetramp.com these
are older production saratov and have proven to be
better then any new production in exsistence. cheers
tt
Those are the tubes I want so I just e-mailed Terry...that's a decent price for a quad.
FWIW, last night I tried the ole cranked-AC30 trick of turning the bass/treble off, volume full up, cut to taste and WOW! It was this thick/warm/woody growl and my 335 was feeding back (in a good way) easily. Nice woody/midrangey feedback...not some high-pitched feedback...good midrange-voiced feedback. The ability to go from twangy and bright to thick and warm is amazing. I wasn't sure if I'd like this tone stack but so far I love it. The range and sweep of the controls is great and the tone/cut controls are still VERY effective when cranked (very often in Marshalls the tone stack becomes very ineffective when cranked). I'll try to make some clips once I get some decent tubes in it.
[quote]If you like more girth in the sound, use the higher voltage tap and a 68 Ohm Cathode resistor. It takes away a slight amount of jangle but, adds midrange "girth"[quote]
By use the higher voltage tap, do you mean the 300v tap on the PT, instead of the 260v tap?
I would like to go in this direction tonally, but what are the issues/concerns with using the 300v tap vs the 260v tap?
Anyone using the 300v tap on the PT for this build?[/quote]
Curbdog,
At the higher plate voltage you'll have to run it at less current (thus the 68ohm Rk). The data sheet says 300vdc max plate and screen voltage but my Velocette originally ran 2 x EL84s at ~375vdc with a shared 120ohm cathode resistor (this amp also used seperate 120ohm screen grid resistors)...it ran the tubes at almost 17W per tube! Tubes survived but did not sound good for very long at all...it was pretty ridiculous how fast it ate tubes. But that's just one experience with one amp. It does seem that the trend among many amps with these tubes is...torture the hell out of 'em.
I can tell you that my amp has plenty of low end and girth...but Allyn said 'midrange-girth' so maybe that's a little different. Also FWIW, when others have compared the Heyboer AC30 OT with the MM Woden clone the consensus was that the Heyboer had too Hi-Fi of a frequency response where the Mercury had richer mids and less of the low lows and high highs. But this group got the TW-spec 5.2K OT which might sound very different than their AC30 OT.
My plan/opinion is that using the 300v tap is not really a consideration. The 300vdc plate voltage (not tap, but actual plate voltage when using the 260v tap) is consistent with both Rockets and AC30s and has proven to yield some of the grail-est of tones. And besides...those taps are buried and I'm too lazy to go back in there unless absolutely necessary. Still...I do hope at least one of the group tries it and posts any findings/opinions.
Fischerman, nice looking build! I noticed you paralleled V1. Have you tried it without? He used V1B for the input as usual and V1A as the driver for the CF. He finished the CF on V2B and left V1A unused on the real ones. I would have done what you did with respects to the CF but, who knows why Ken did it that way?
Hi Allyn,
I did notice that KF did the second stage on V1...but if I'm not mistaken he used the second B+ node for the second stage B+ (in other words...the second stage and CF still share the same B+ node and the input stage gets a node all to itself). As to why he did it the way he did...I have no idea other than that's the way the Liverpool and Express are wired.
Regarding paralleling the V1 triodes...I haven't tried it the 'normal' non-paralleled way yet but I fully intend to. I want to get to know the amp better first though...so I'm more tuned in to the more subtle things. I'm still in the honeymoon phase! I haven't even 'scoped it yet...hope to do that tonight.
FWIW, here is an interesting article by Steve Bench on the subject. Sites like Steve's and Ken Gilbert's usually go over my head but there's usually some stuff in there that's been dumbed down enough for me. Guys like that have forgotten more than I'll ever know about these things. Cliff notes on Steve's article is that paralleling is more likely to sound worse than better because lower order harmonics are attenuated and higher order harmonics are increased.
Oh, and thanks for the kind words everyone. This amp already one of my favorite builds.
And a big thanks to RJ for putting it all together. I know you put a ton of work into this Bob and I appreciate it. Heck...just boxing everything up for shipment was a quite a job in and of itself (nice packing job too BTW).
I'm already looking ahead at possibly a Rocket or 'Pool with VVR...or maybe the two-channel 'Wreck...with VVR.
Great news...I got a tracking nubmer todays..its on its way. Nice build Fischerman I would love to hear it. Thanks for posting the pics really nice.For future reference I like the the 2 channel wreck ideas as well. I am not a vvr kind of guy though. I have never heard one I felt did the amp any justice. They seem to fart out to me and get that phaser type sound ...like when a power tube is on the fritz or there is a short dragging your bias down. I havent heard them all though but I am not particularly fond thus far. I would rather just build a low watter and leave it at that and then a high watter for gigging etc..thats just me though. I would love to hear a great one I guess.
), 200uF cathode cap/25uF cathode cap are Sprague Atom 50v, and the black dual cap is an F&T 33uFx2/450v. My treble cap is a parallel combo of a 47pF Murata ceramic and a CD 10pF silver mica (I guess I figured that being a little high was better than being a little low 
). I used the Heyboer PT and Dagnall choke that RJ bought for the group but used a Mercury Magnetics Woden clone OT (it only has 8 and 16 ohm taps). I used a fused IEC connector for the mains and then used the fuse holder for the HT fuse. I paralleled the triodes in the first tube for the input stage (and adjusted the values...this is all a test to see which way I like best...values/paralleling may change 
) and then used Marshall-style wiring on V2 (except reversed the triodes). And of course the layout is different. Other than that it's exactly like a Rocket. 
